Coulomb

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The coulomb (symbol: C) is the SI unit of electric charge. It is named after Charles-Augustin de Coulomb (1736 to 1806).

Contents 1 Definition 2 Explanation 3 Historical note 4 SI multiples 5 Conversions 6 See also

Definition

1 coulomb is the amount of electric charge carried by a current of 1 ampere flowing for 1 second.

<math> 1 \ \mathrm{C} = 1 \ \mathrm{A} \cdot \mathrm{s}</math>

Explanation

The coulomb is also the unit of electric flux. (See Gauss Law).

The coulomb could in principle be defined in terms of the charge of an electron or elementary charge. Since the values of the Josephson (CIPM (1988) Recommendation 1, PV 56; 19) and von Klitzing (CIPM (1988), Recommendation 2, PV 56; 20) constants have been given conventional values (K_J ≡ 4.835 979Template:E Hz/V and R_K ≡ 2.581 280 7Template:E Ω), it is possible to combine these values to form an alternative (not yet official) definition of the coulomb. A coulomb is then equal to exactly 6.241 509 629 152 65Template:E elementary charges. Combined with the current definition of the ampere, this proposed definition would make the kilogram a derived unit.

Historical note

The ampere was historically a derived unit - being defined as 1 coulomb per second. Therefore the coulomb, rather than the ampere was the SI base electrical unit,

Recently (1960) the SI system made the ampere the base unit (See http://alpha.montclair.edu/~kowalskiL/SI/SI_PAGE.HTML).

SI multiples

Template:SI multiples

Conversions

• One mole of electrons (approximately 6.022Template:E, or Avogadro's number) is known as a faraday (actually -1 faraday, since electrons are negatively charged). One faraday equals 96.485 341 5 kC (the Faraday constant). In terms of Avogadro's number (N_A), one coulomb is equal to approximately 1.036 × N_A Template:E elementary charges.

• one ampere-hour = 3600 C

• The elementary charge is approximately 160.2176 zC.

• One statcoulomb (statC), the CGS electrostatic unit of charge (esu), is approximately 3.3356Template:E C or about 1/3 nC.

• 1 coulomb is the amount of electrical charge in 6.241Template:E electrons or other elementary charged particles.

See also

• Coulomb's law
• Current (electricity)
• Faraday constant
• Quantity of electricity
• SI
• Amperear:كولوم

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